correct code styles to conform to the ESLint rules

[Zh40Le1ZOOB]

Description

Some incorrect code styles will cause errors when build:

    ERROR in [eslint] 1337;CurrentDir=/build/source
      ✘  http://eslint.org/docs/rules/no-trailing-spaces   Trailing spaces not allowed         
      src/renderer/components/Task/TaskItem.vue:37:1

      ✘  http://eslint.org/docs/rules/keyword-spacing      Expected space(s) after "if"        
      src/renderer/components/Task/TaskList.vue:56:9

      ✘  http://eslint.org/docs/rules/space-before-blocks  Missing space before opening brace  
      src/renderer/components/Task/TaskList.vue:56:42

    ✘ 3 problems (3 errors, 0 warnings)

So I corrected code following ESLint rules that provided in the error output.

Checklist:

• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Have you linted your code locally prior to submission?
• [x] Have you successfully ran app with your changes locally?